Transparent conductor

ABSTRACT

A transparent conductor includes a film-shaped or plate-shaped support and a transparent conductive layer that is disposed on the support and has a surface formed as a rough surface. The surface of the transparent conductive layer is formed so that a maximum peak height that shows a surface roughness of the surface is in a range of 0.35 μm to 0.43 μm, inclusive.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transparent conductor where atransparent conductive layer is disposed on a film-shaped orplate-shaped support.

2. Description of the Related Art

As one example of this type of transparent conductor, a transparentelectrode (the outer transparent electrode that is touched) used in atouch panel disclosed by Japanese Laid-Open Patent Publication No.H11-250764 is known. This transparent electrode is constructed of atransparent resin film and a transparent thin-film electrode layer thatis laminated on the transparent resin film. To prevent Newton's rings(interference fringes) from being produced when the transparentelectrode is touched with a finger or a pen, the surface of thetransparent thin-film electrode layer is formed with a surface roughnesswithin a predetermined range. The “center line average roughness” and“maximum height” that show the surface roughness of the transparentelectrode are respectively set in a range of 0.05 μm to 2 μm, inclusive,and in a range of 0.6 μm to 2.5 μm, inclusive.

SUMMARY OF THE INVENTION

By investigating the transparent electrode described above, the presentinventors found the following problem. That is, with the abovetransparent electrode, by forming the surface of the transparentthin-film electrode layer so that the center line average roughness andmaximum height thereof are in the respective ranges described above, itis possible to avoid the production of Newton's rings. However, evenwhen the center line average roughness and maximum height are within theset ranges, for example, if the parts that protrude from the center line(average line) (hereinafter such parts are referred to as “peaks”) arehigh, when the transparent thin-film electrode layer is incorporated ina touch panel and touch operations are repeatedly performed, the surfaceof the transparent thin-film electrode layer of an inner transparentelectrode disposed on the display side opposite the outer transparentelectrode can be damaged by the peaks. In this type of touch panel, whenthe surface of a transparent thin-film electrode layer is damaged, theresistance of the transparent thin-film electrode layer changes,resulting in a problem that it can be difficult to specify a touchedposition.

The present invention was conceived in view of the problem describedabove, and it is a principal object of the present invention to providea transparent conductor that can prevent Newton's rings from beingproduced and can reduce the incidence of damage.

To achieve the stated object, a transparent conductor according to thepresent invention includes: a film-shaped or plate-shaped support; and atransparent conductive layer that is disposed on the support and has asurface formed as a rough surface, wherein the surface of thetransparent conductive layer is formed so that a maximum peak heightthat shows a surface roughness of the surface is in a range of 0.35 μmto 0.43 μm, inclusive.

According to the above transparent conductor, the transparent conductivelayer is formed so that a maximum peak height that shows a surfaceroughness of the surface is in a range of 0.35 μm to 0.43 μm, inclusive.With this construction, light is appropriately scattered, and thereforethe production of Newton's rings can be reliably avoided. Also, unlike aconventional transparent conductor where the maximum peak height islarge, by setting the maximum peak height in a range of 0.35 μm to 0.43μm, inclusive, the heights of the peaks can be averaged, so that when anupper electrode and a lower electrode slide against each other, thepressure is distributed among the peaks and it is therefore possible toreliably reduce damage to the surfaces. Accordingly, with a touch panelin which the transparent conductor described above is incorporated, itis possible to reliably prevent the production of Newton's rings and tosufficiently improve durability.

Another transparent conductor according to the present inventionincludes: a film-shaped or plate-shaped support; and a transparentconductive layer that is disposed on the support and has a surfaceformed as a rough surface, wherein the surface of the transparentconductive layer is formed so that a maximum valley depth that shows asurface roughness of the surface is in a range of 1.03 μm to 2.37 μm,inclusive.

According to the above transparent conductor, the transparent conductivelayer is formed so that a maximum valley depth that shows a surfaceroughness of the surface is in a range of 1.03 μm to 2.37 μm, inclusive.With this construction, light is appropriately scattered, and thereforethe production of Newton's rings can be reliably avoided. Also, unlike aconventional transparent conductor where the maximum valley depth issmall, by setting the maximum valley depth in a range of 1.03 μm to 2.37μm, inclusive, it is possible to reduce the number of peaksproportionate to the increase in the number of valleys, so that when anupper electrode and a lower electrode slide against each other, it ispossible to reliably reduce damage to the surfaces. Accordingly, with atouch panel in which the transparent conductor described above isincorporated, it is possible to reliably prevent the production ofNewton's rings and to sufficiently improve durability.

Yet another transparent conductor according to the present inventionincludes: a film-shaped or plate-shaped support; and a transparentconductive layer that is disposed on the support and has a surfaceformed as a rough surface, wherein the surface of the transparentconductive layer is formed so that a maximum peak height that shows asurface roughness of the surface is in a range of 0.35 μm to 0.43 μm,inclusive and a maximum valley depth that shows the surface roughness ofthe surface is in a range of 1.03 μm to 2.37 μm, inclusive.

According to the above transparent conductor, the transparent conductivelayer is formed so that a maximum peak height that shows a surfaceroughness of the surface is in a range of 0.35 μm to 0.43 μm, inclusiveand a maximum valley depth that shows the surface roughness of thesurface is in a range of 1.03 μm to 2.37 μm, inclusive. With the aboveconstruction, it is possible to average the heights of the peaks and toreduce the number of peaks proportionate to the increase in the numberof valleys, and therefore the pressure can be distributed among thepeaks when an upper electrode and a lower electrode slide against eachother and the frequency of contact between the peaks and the surface ofthe lower electrode can be reduced. As a result, it is possible toreduce damage to the surfaces more reliably. Accordingly, with a touchpanel in which the transparent conductor described above isincorporated, it is possible to reliably reduce the production ofNewton's rings and to significantly improve durability.

Here, the transparent conductive layer may be constructed by compressingconductive fine particles. With this construction, it is possible toincrease the points of contact between the conductive fine particles andto increase the contact area, thereby increasing the strength of thetransparent conductive layer and improving the light transmittance ofthe transparent conductive layer. Also, unlike a conventional method ofmanufacturing that applies a coating composition including conductivefine particles and binder (resin) when forming the transparentconductive layer, it is possible to form the transparent conductivelayer by applying a coating composition (dispersion liquid) that doesnot include resin and then compressing conductive fine particles, andtherefore it is possible to reduce the probability of a fall inconductivity due to contact between the conductive fine particles beingobstructed by the binder.

It should be noted that the disclosure of the present invention relatesto a content of Japanese Patent Application 2005-191886 that was filedon 30 Jun. 2005 and the entire content of which is herein incorporatedby reference.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will beexplained in more detail below with reference to the attached drawings,wherein:

FIG. 1 is a cross-sectional view of a transparent conductive film;

FIG. 2 is a cross-sectional view of a transfer film;

FIG. 3 is a cross-sectional view of a recipient film;

FIG. 4 is a cross-sectional view of a state where the transfer film andthe recipient film have been placed in tight contact;

FIG. 5 is a cross-sectional view of a state where a base film and ananchor layer have been detached from a transparent conductive layer;

FIG. 6 is a measurement results table showing measurement results forvarious transparent conductive films;

FIG. 7 is a figure-substitute photograph of the surface of a transparentconductive film;

FIG. 8 is a figure-substitute photograph of the surface of anothertransparent conductive film;

FIG. 9 is a figure-substitute photograph of the surface of yet anothertransparent conductive film; and

FIG. 10 is a figure-substitute photograph of the surface of yet anothertransparent conductive film.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of a transparent conductor according to thepresent invention will now be described with reference to the attacheddrawings.

First, the construction of a transparent conductive film 1 will bedescribed with reference to the drawings.

The transparent conductive film 1 shown in FIG. 1 is one example of atransparent conductor according to the present invention and includes asupport 2, a resin layer 3, and a transparent conductive layer 4. Notethat the term “transparent” for the present invention means that visiblelight can be transmitted and includes a state where some scattering oflight occurs. Here, the extent to which light is scattered differsaccording to the intended use of the transparent conductive film 1 witha level of scattering normally referred to as “semi-transparent” alsoincluded in the term “transparent” for the present invention.

The support 2 is formed in a film-like form or plate-like form using atransparent material such as resin or glass. As examples of the resinmaterial that constitutes the support 2, it is possible to use apolyester resin such as polyethylene terephthalate (PET), a polyolefinresin such as polyethylene or polypropylene, polycarbonate, acrylic,norbornene, and the like. The resin layer 3 is a transparent layerformed on the surface of the support 2 and is formed according to amethod described later. The transparent conductive layer 4 istransparent and conductive and is formed (disposed) on the surface ofthe support 2 via the resin layer 3. The transparent conductive layer 4is formed according to a method described later, and a surface 41thereof is formed as a rough surface. Here, the surface 41 of thetransparent conductive layer 4 is formed so that a maximum peak heightSp that shows the surface roughness is in a range of 0.35 μm to 0.43 μm,inclusive and a maximum valley depth Sv that also shows the surfaceroughness is in a range of 1.03 μm to 2.37 μm, inclusive.

Next, the method of manufacturing the transparent conductive film 1 willbe described with reference to the drawings.

First, as shown in FIG. 2, a transfer film 10 where a base film 5, ananchor layer 6, and the transparent conductive layer 4 are laminated inthe mentioned order is fabricated. The transfer film 10 is a film fortransferring the transparent conductive layer 4 onto a recipient film 20(see FIG. 3) described later, and after the transparent conductive layer4 has been transferred, the base film 5 and the anchor layer 6 aredetached from the transparent conductive layer 4. As one example, thebase film 5 is composed of resin containing fine inorganic particlessuch as silicon oxide (SiO₂) in a film shape. Fine concaves and convexesthat reflect the form of the fine particles are formed in the surface ofthe base film 5. The anchor layer 6 functions so as to temporarily fix(attach) the transparent conductive layer 4 to the base film 5.

When the transfer film 10 is fabricated, first, a coating composition(for example, a coating composition including silicone resin) forforming the anchor layer 6 is applied onto the base film 5. Here, it ispossible to use various well-known application methods as the method ofapplying the coating composition onto the base film 5. Morespecifically, when the coating composition has a high viscosity of 1000cps or higher, for example, it is possible to use a method that uses ablade, knife, or the like. Conversely, when the coating composition hasa low viscosity of below 500 cps, a method such as bar coating, kisscoating, squeezing, or a method that uses a mist or spray can be used.In addition, regardless of the viscosity of the coating composition, itis possible to use methods such as reverse rolling, direct rolling,extrusion via a nozzle, curtaining, gravure rolling, and dipping. Next,the coating composition applied onto the base film 5 is dried. By doingso, the anchor layer 6 is formed on the surface of the base film 5.

Next, a dispersion liquid for forming the transparent conductive layer 4is fabricated. First, by carrying out a well-known dispersion methodusing a sand grinder mill or a ball mill, conductive fine particles(dispersoid) are dispersed in a dispersion medium to produce thedispersion liquid. As the conductive fine particles, it is possible touse various types of fine particles that can form the transparentconductive layer 4 that is transparent and conductive. As examples, fineparticles of tin oxide such as antimony-doped tin oxide (ATO) andfluorine-doped tin oxide (FTO), fine particles of indium oxide such astin-doped indium oxide (ITO), fine particles of zinc oxide such asaluminum-doped zinc oxide (AZO), and fine particles of cadmium oxide canbe used. Here, ITO is preferable since superior conductivity isachieved. As the conductive fine particles, it is also possible to useparticles produced by coating the surfaces of transparent fineparticles, such as barium sulfate, with ATO, ITO, or the like. Theparticle diameter of the fine particles can be freely set in accordancewith the level of scattering of light required in accordance with theintended use of the transparent conductive film 1, and is typically setin a range of 1.0 μm or below (more preferably, in a range of 0.1 μm orbelow, and even more preferably in a range of 5 nm to 50 nm, inclusive).

It is also possible to produce the dispersoid by treating the surfacesof the conductive fine particles described above with an inorganicsubstance. Here, as one example, a silicon compound (such as silicondioxide SiO₂ (including SiO_(2-X) containing a few oxygen defects)) canbe used as the inorganic substance used for the surface treatment. Here,by treating the surfaces of the conductive fine particles with aninorganic substance, it is possible to improve the durability of thetransparent conductive layer 4 that is formed by compression, andtherefore the stability of the electrical resistance over time in a hightemperature/high humidity environment is improved.

On the other hand, it is possible to use various well-known liquids asthe dispersion medium in which the conductive fine particles aredispersed. More specifically, it is possible to use a saturatedhydrocarbon such as hexane, an aromatic hydrocarbon such as toluene andxylene, an alcohol such as methanol, ethanol, propanol, and butanol, aketone such as acetone, methyl ethyl ketone, methyl isobutyl ketone, anddiisobutyl ketone, an ester such as ethyl acetate and butyl acetate, anether such as tetrahydrofuran, dioxane, and diethyl ether, an amide suchas N,N-dimethylformamide, N-methylpyrrolidone (NMP), andN,N-dimethylacetamide, and a halogenated hydrocarbon such as ethylenechloride and chlorobenzene. Out of such dispersion media, polarizeddispersion media are preferable, and hydrophilic dispersion media suchas alcohols (methanol, ethanol, or the like) or amides (NMP or the like)are more preferable since favorable dispersion can be achieved withoutmixing in a dispersing agent. Such dispersion media may be used alone,or a mixture of two or more such media may be used. It is also possibleto use a dispersing agent in accordance with the type of dispersionmedia used. Also, although water can be used as the dispersion medium,to make the thickness of the transparent conductive layer 4 uniform, thesupport 2 needs to be hydrophilic. Accordingly, when a resin film thatis normally hydrophobic is used as the support 2, a hydrophilic alcoholshould preferably be mixed with the water. Here, the amount ofdispersion medium used to disperse the conductive fine particles can beadjusted as appropriate to produce a suitable viscosity for applicationof the dispersion liquid after dispersion.

Next, the dispersion liquid is applied onto the anchor layer 6. Here, asthe method of applying the dispersion liquid, it is possible to use thesame types of methods as are used to form the base film 5. Next, byusing a drying apparatus, the base film 5 on which the dispersion liquidis applied is dried at a suitable drying temperature for the type ofdispersion medium used. By doing so, the dispersion medium in thedispersion liquid evaporates and a conductive fine particle layer isformed by the conductive fine particles (dispersoid) that have beencondensed. Next, the conductive fine particle layer is compressed usinga sheet press or a roll press. When doing so, the compression forceapplied to the conductive fine particle layer should preferably be44N/mm² or higher, more preferably 135N/mm² or higher, and even morepreferably 180N/mm².

By doing so, the transparent conductive layer 4 is formed on the anchorlayer 6. Here, in this method of manufacturing, since the conductivefine particle layer is compressed, there is an increase in the number ofpoints of contact between the conductive fine particles and the contactarea is increased, resulting in an increase in the strength of thetransparent conductive layer 4 and an improvement in light transmittanceby the transparent conductive layer 4. Also, with this method ofmanufacturing, it is possible to form the transparent conductive layer 4without adding a resin that was added as a binder in the conventionalmethod of manufacturing. This means that there is less probability ofcontact between conductive fine particles being obstructed by thebinder, which would result in lower conductivity. Note that additivessuch as a UV absorber, a surfactant, and a dispersing agent may also beadded within a range where no fall in the conductivity of thetransparent conductive layer 4 is caused.

Next, as shown in FIG. 3, a recipient film 20 where the resin layer 3 islaminated on the support 2 is fabricated. More specifically, a coatingcomposition for forming the resin layer 3, which has been produced bydissolving resin in a solvent, is applied onto the support 2. Here, asexamples, an organic polymer such as a fluorine polymer, silicone resin,acrylic resin, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylcellulose, regenerated cellulose, diacetyl cellulose, polyvinylchloride, polyvinyl pyrrolidone, polyethylene, polypropylene, SBR,polybutadiene, polyethylene oxide, polyester, and polyurethane, or aprecursor (monomer, oligomer) of the same can be used as the resin.Also, as the solvent for dissolving the resin, it is possible to use asaturated hydrocarbon such as hexane, an aromatic hydrocarbon such astoluene and xylene, an alcohol such as methanol, ethanol, propanol, andbutanol, a ketone such as acetone, methyl ethyl ketone, methyl isobutylketone, and diisobutyl ketone, an ester such as ethyl acetate and butylacetate, an ether such as tetrahydrofuran, dioxane, and diethyl ether,an amide such as N,N-dimethylformamide, N-methylpyrrolidone (NMP), andN, N-dimethylacetamide, a halogenated hydrocarbon such as ethylenechloride and chlorobenzene, and water. The resin layer 3 functions as anadhesion layer that binds (causes adhesion between) the support 2 andthe transparent conductive layer 4. For this reason, an electron beam(UV ray) curable resin is preferably added to the coating composition sothat the resin can be hardened by an electron beam such as UV rays. Asthe method of hardening the resin, it is also possible to use awell-known method such as adding a reactive group to the resin describedabove. In addition, it is possible to add additives such as a UVabsorber, an IR absorber, and a colorant to the coating composition.

On the other hand, as the method of applying the coating compositiondescribed above onto the support 2, it is possible to use a well-knownmethod such as reverse rolling, direct rolling, a method that uses ablade or a knife, extrusion via a nozzle, curtaining, gravure rolling,bar coating, dipping, kiss coating, and squeezing. It is also possibleto use a method of appling the coating composition onto the support 2using a mist or a spray. Next, the applied coating composition is driedto vaporize the solvent. By doing so, the resin layer 3 is laminated(formed) on the support 2.

Next, as shown in FIG. 4, the transfer film 10 is placed over therecipient film 20 so that the transparent conductive layer 4 of thetransfer film 10 and the resin layer 3 of the recipient film 20 are intight contact. At this time, the resin that forms the resin layer 3permeates into (and fills) the voids between the conductive fineparticles that constitute the transparent conductive layer 4. Next, asone example, when a UV ray curable resin has been added to the coatingcomposition for forming the resin layer 3, UV rays are irradiated fromoutside (the upper side in FIG. 4) the base film 5 of the transfer film10 to harden the resin layer 3 and the resin constituting the resinlayer 3 that has permeated into the voids in the transparent conductivelayer 4. Next, the base film 5 is detached. When doing so, since thecontact between the anchor layer 6 and the base film 5 is tighter thanthe contact between the anchor layer 6 and the transparent conductivelayer 4, as shown in FIG. 5, the anchor layer 6 is detached from thetransparent conductive layer 4 together with the base film 5. By doingso, as shown in FIG. 1, the transparent conductive layer 4 istransferred via the resin layer 3 onto the support 2 to manufacture thetransparent conductive film 1 where the transparent conductive layer 4is exposed. Here, when the thickness of the transparent conductive layer4 is below 0.1 μm, there is a risk of an increase in electricalresistance and a fall in the electrical properties of the transparentconductive film 1. On the other hand, if the thickness of thetransparent conductive layer 4 exceeds 5 μm, there is a risk of a fallin overall light transmission and a loss in transparency. For thisreason, the thickness of the transparent conductive layer 4 shouldpreferably be in a range of 0.1 μm to 5 μm, inclusive.

Next, the characteristics of transparent conductive films 1A to 1Cmanufactured in the manufacturing procedure described below according tothe method of manufacturing described above and the characteristics of atransparent conductive film 1D for comparison purposes manufacturedaccording to a method of manufacturing described later will bedescribed.

The manufacturing procedure of the transparent conductive film 1A willbe described first. As shown in FIG. 2, first a transfer film 10A onwhich the base film 5A, the anchor layer 6A, and the transparentconductive layer 4A have been laminated in the mentioned order wasfabricated. In more detail, after a coating composition for forming theanchor layer 6A was applied on the surface of the base film 5A, dryingwas carried out for 24 hours at 70° C. to harden the coating compositionand thereby form the anchor layer 6A with a thickness of 1 μm. Here, PETfilm (“X42” manufactured by Toray industries Inc.) with a thickness of26 μm and an arithmetic average height Sa, which shows the surfaceroughness, of 0.4 μm was used as the base film 5A. Silicone resin (amixture of 100 parts by weight of liquid A and 300 parts by weight ofliquid B of “Frecera N” manufactured by Matsushita Electric Works, Ltd.)was used as the coating composition for forming the anchor layer 6A.

Next, 300 parts by weight of ethanol were added to 100 parts by weightof ITO fine particles (“SUFP-HX” (primary particle diameter: 20 nm) madeby Sumitomo Metal Mining Co., Ltd.) and dispersing was carried out usinga ball mill to fabricate a coating composition for forming thetransparent conductive layer 4A. Here, zirconia beads were used as thedispersion medium. Next, after the coating composition for forming thetransparent conductive layer 4A was applied onto the anchor layer 6Ausing a bar coater, the coating composition was dried by blowing warmair at 50° C., thereby forming an coating film that includes ITO and hasa thickness of 1.7 μm (the film in this state is also referred to as the“pre-compression transfer film”).

Next, a preliminary test was carried out to confirm the compressionpressure. More specifically, a roll press equipped with a pair of metalrolls with a diameter of 140 mm and surfaces that have been hard chromeplated was used, and the pre-compression transfer film was squeezed andcompressed at a temperature of 23° C. in a state where the metal rollswere not rotated. When doing so, the pressure per unit length in thewidthwise direction of the film was set at 660N/mm. Next, the pressurewas released and the length in the lengthwise direction of thecompressed part of the pre-compression transfer film was measured. As aresult, the length in the lengthwise direction of such part was found tobe 1.9 mm. From this result, it was understood that a pressure of347N/mm² per unit area had been applied. Next, the pre-compressiontransfer film was compressed between the metal rolls according to thesame conditions as the preliminary test described above, the rolls wererotated, and the pre-compression transfer film was compressed at a feedspeed of Sm/min. By doing so, the transfer film 10A was obtained. Here,when measured using an electronic micrometer (K-402B) made by AnritsuCorp., the thickness of the transparent conductive layer 4A was found tobe 1.0 μm.

Next, as shown in FIG. 3, a recipient film 20A on which the support 2Aand the resin layer 3A have been laminated was fabricated. Morespecifically, 184 parts by weight of methyl ethyl ketone were added as asolvent to 100 parts by weight of acrylic resin (“1BR-305” (solidcontent: 39.5%) made by Taisei Kako Co., Ltd.) and 92 parts by weight ofWV ray curable resin (“SD-318” made by Dainippon Ink and Chemicals,Inc.) to fabricate the coating composition for forming the resin layer3A. Next, after the coating composition for forming the resin layer 3Awas applied onto a PET film (thickness: 188 μm) as the support 2A, thesolvent was vaporized to form the resin layer 3A with a thickness of 8μm, thereby producing the recipient film 20A. Next, as shown in FIG. 4,the transfer film 10A was placed over the recipient film 20A so that thetransparent conductive layer 4A of the transfer film 10A and the resinlayer 3A of the recipient film 20A were in tight contact. By doing so,the transparent conductive layer 4A was laminated on the resin layer 3Aand the mixture of the acrylic resin and the UV ray curable resin thatcomposes the resin layer 3A (this mixture is hereinafter also referredto as the “UV curable resin etc.”) was caused to permeate into the voidsin the transparent conductive layer 4A.

Next, UV rays were irradiated from outside the base film 5A of thetransfer film 10A to harden the resin layer 3A and the UV curable resinetc. that had permeated into the voids in the transparent conductivelayer 4A. Next, as shown in FIG. 5, the base film 5A and the anchorlayer 6A were detached from the transparent conductive layer 4A. Bydoing so, as shown in FIG. 1, the transparent conductive layer 4A wastransferred via the resin layer 3A onto the support 2A, therebyproducing the transparent conductive film 1A on which the transparentconductive layer 4A was exposed.

Next, the manufacturing procedure of the transparent conductive film 1Bwill be described. As shown in FIG. 2, first the transfer film 10B onwhich the base film 5B, the anchor layer GB, and the transparentconductive layer 4B have been laminated in the mentioned order wasfabricated using the same procedure as the transfer film 10A describedabove. When doing so, the anchor layer 6B was formed with a thickness of0.5 μm using the same coating composition as the anchor layer 6Adescribed above. Aside from this, the same materials as were used tofabricate the transfer film 10A were used to form the transparentconductive layer 4B with a thickness of 1.0 μm. Next, as shown in FIG.3, the recipient film 20B on which the support 2B and the resin layer 3Bhave been laminated was fabricated using the same procedure as whenfabricating the recipient film 20A described above. After this, as shownin FIG. 4, the transfer film 10B was placed over the recipient film 20Band UV rays were irradiated from outside the base film 5B of thetransfer film 10B to harden the resin layer 3B and the UV curable resinetc. that had permeated into the voids in the transparent conductivelayer 4B. Next, as shown in FIG. 5, the base film 5B and the anchorlayer 6B were detached to produce the transparent conductive film 1B.

Next, the manufacturing procedure of the transparent conductive film 1Cwill be described. As shown in FIG. 2, first the transfer film 10C onwhich the base film 5C, the anchor layer 6C, and the transparentconductive layer 4C have been laminated in the mentioned order wasfabricated using the same procedure as the transfer film 10A describedabove. Here, PET film (“X43” manufactured by Toray industries Inc.) witha thickness of 26 μm and an arithmetic average height Sa, which showsthe surface roughness, of 0.35 μm was used as the base film 5C. Theanchor layer 6C was formed with a thickness of 0.5 μm using the samecoating composition as the anchor layer 6A described above. Aside fromthis, the same materials as were used to fabricate the transfer film 10Awere used to form the transparent conductive layer 4C with a thicknessof 1.0 μm. Next, as shown in FIG. 3, the recipient film 20C on which thesupport 2C and the resin layer 3C have been laminated was fabricatedusing the same procedure as when fabricating the recipient film 20Adescribed above. After this, as shown in FIG. 4, the transfer film 10Cwas placed over the recipient film 20C and UV rays were irradiated fromoutside the base film 5C of the transfer film 10C to harden the resinlayer 3C and the UV curable resin etc. that had permeated into the voidsin the transparent conductive layer 4C. Next, as shown in FIG. 5, thebase film 5C and the anchor layer 6C were detached to produce thetransparent conductive film 1C.

Next, the method of manufacturing the transparent conductive film 1D forcomparison purposes will be described. First, one surface of a PET filmwith a thickness of 188 μm and a width of 350 mm was embossed to producea support 2D. When doing so, the embossing was carried out using a rollwith a surface that has been formed by laser engraving so that anarithmetic average height Sa and a maximum cross-sectional height St are1.9 μm and 35.8 μm, respectively and chrome plated. As the rolling(pressing) conditions, the pressure applied by the press (linearpressure) was set at 35 Kg/cm, the press temperature (the surfacetemperature of the metal roll) at 175° C. and the press speed at 3m/min. When the surface roughness of the support 2D subjected to theembossing was measured, the arithmetic average height Sa and the maximumcross-sectional height St were 0.14 μm and 2.78 μm, respectively. Next,the surface of the support 2D that has been embossed was subjected to acorona discharge treatment. After this, a sol-gel solution produced bymixing 6 mol of water, 6 mol of ethyl alcohol and 0.03 mol ofhydrochloric acid into 1 mol of tetraethoxysilane was roll-coated ontothe surface of the support 2D. Next, hot air was blown onto the surfaceof the support 2D to cause the solvent to evaporate and then the support2D was further heated to form a thin film of silica dioxide. After this,ITO was sputtered onto the thin film of silica dioxide to form thetransparent conductive layer 4D with a thickness of 25 nm. By doing so,the transparent conductive film 1D where the transparent conductivelayer 4D is formed via a thin film of silica dioxide on the support 2Dwas obtained.

Next, the arithmetic average height Sa and the maximum peak height Spthat show the surface roughness were measured for the transparentconductive layers 4A to 4D of the fabricated transparent conductivefilms 1A to 1D using a three-dimensional non-contact surface mappingsystem (Micromap) made by Micromap Corp. of America. The measurementconditions were as follows.

Measurement Mode: Wave Mode

Measurement Area: 640×480 pixels

Magnification: 10 times

Analysis Conditions: Detrending Correction=Plane FILL=On

-   -   Median Filter: Xwindow=5, Ywindow=5    -   Smooth Filter: Xwindow=5, Ywindow=5

As a result, as shown in FIG. 6, it was found that the arithmeticaverage heights Sa of the transparent conductive layers 4A to 4D of thefabricated transparent conductive films 1A to 1D were respectively 0.10μm, 0.12 μm, 0.16 μm, and 0.11 μm. On the other hand, as shown in thesame drawing, the maximum peak heights Sp of the transparent conductivelayers 4A to 4D were respectively 0.35 μm, 0.43 μm, 0.41 μm, and 1.66μm.

Next, touch panels 30A to 30D (generically referred to as the “touchpanel 30” when no distinction is required) that use the transparentconductive films 1A to 1D were fabricated. Here, transparent conductorswhere a covering film of ITO (a transparent conductive layer) was formedon a glass substrate and dot-shaped nonconductive spacers were disposedin a matrix on the covering film were used as the respective lowerelectrodes. The transparent conductive films 1A to 1D were used as therespective upper electrodes. Next, a touch pen made of polyacetal whosetip was spherically (or hemispherically) formed with a diameter of 0.8mm was used to press (touch) 20 positions on the upper electrodes (thetransparent conductive films 1A to 1D) of the touch panels 30A to 30D,respectively and it was visually observed whether Newton's rings(interference fringes) and glare were produced. As a result, as shown inFIG. 6, it was not possible to observe Newton's rings and the like atany of the pressed positions for the touch panels 30A to 30D. From theseresults, it is clear that when the maximum peak height Sp of the surface41 of the transparent conductive layer 4 is in a range of 0.35 μm to 1.6μm, inclusive, light is suitably scattered and the production ofNewton's rings and the like is reliably prevented. It is conventionallyknown that the production of Newton's rings and the like is preventedwhen the arithmetic average height Sa of the surface 41 of thetransparent conductive layer 4 is in a range of 0.05 μm to 0.35 μm,inclusive, and from the results described above, it is clear that theproduction of Newton's rings and the like is reliably prevented when thearithmetic average height Sa is in a range of 0.10 μm to 0.16 μm,inclusive.

Next, in a state where the pen tip has pressed the surface of the upperelectrodes of the respective touch panels 30A to 30D toward the lowerelectrodes, the pen tip was moved back and forth to cause the upperelectrodes and the lower electrodes to slide against each other and thepercentage change in resistance of the lower electrode before and afterdoing so was measured. A 250 g load was added to the touch pen and thepen tip was moved back and forth 150,000 times. As a result, as shown inFIG. 6, with the touch panels 30A to 30C that use the transparentconductive films 1A to 1C, the percentage changes in resistance of thelower electrodes were 1.5%, 2.3%, and 2.5%, respectively, but with thetouch panel 30D that uses the transparent conductive film 1D, thepercentage change in resistance was as high as 12%. From thesemeasurement results, it is clear that even if the arithmetic averageheight Sa of the surface 41 of the transparent conductive layer 4 is lowas with the transparent conductive film 1D (here, 0.11 μm), when themaximum peak height Sp is high (here, 1.66 μm), when the upper electrodeand the lower electrode slide against each other, the pressure isconcentrated at the peaks (convex parts) thereof, resulting in damage tothe surface 41 of the transparent conductive layer 4 and a large changein resistance. Conversely, if the maximum peak height Sp is in a rangeof 0.35 μm to 0.43 μm, inclusive, the heights of the peaks are averagedand when the upper electrode and lower electrode slide against eachother, the pressure is distributed among the peaks, resulting in lessdamage to the surface 41 and a smaller change in resistance.

Next, the maximum valley depth Sv and the maximum cross-sectional heightSt that show the surface roughness of the respective transparentconductive layers 4A to 4D of the transparent conductive films 1A to 1Dwere measured using the three-dimensional non-contact surface mappingsystem described above with the same measurement conditions as describedabove. As a result, as shown in FIG. 6, the absolute values of themaximum valley depths Sv of the respective transparent conductive layers4A to 4D were respectively 2.37 μm, 2.06 μm, 1.03 μm, and 0.22 μm. Onthe other hand, as shown in the same drawing, the maximumcross-sectional heights St of the transparent conductive layers 4A to 4Dwere respectively 2.72 μm, 2.49 μm, 1.44 μm, and 1.88 μm. Next, as shownin FIGS. 7 to 10, the surfaces of the transparent conductive layers 4Ato 4D of the transparent conductive films 1A to 4D were mapped using thethree-dimensional non-contact surface mapping system described above.From these surface maps, it is clear that when the maximum valley depthSv is in a range of 1.03 μm to 2.37 μm, inclusive as with thetransparent conductive films 1A to 1C, the higher the number of valleys,the lower the number of peaks that protrude from the average surface. Onthe other hand, it is clear that when the maximum valley depth Sv is lowas with the transparent conductive film 1D (here, 0.22 μm), even if themaximum cross-sectional height St is comparatively small (here, 1.88μm), a large number of peaks protrude from the average surface.Accordingly, from the surface maps and the measurement results describedabove, it is clear that when the maximum valley depth Sv is small, whenthe upper electrode and the lower electrode slide against each other, alarge number of peaks damage the surface 41 of the transparentconductive layer 4, resulting in a large change in resistance. On theother hand, when the maximum valley depth Sv is in a range of 1.03 μm to2.37 μm, inclusive, there are few peaks and therefore when the upperelectrode and the lower electrode slide against each other, there isless damage to the surface 41 and less change in resistance.

Here, when the maximum peak height Sp of the surface 41 of thetransparent conductive layer 4 is in a range of 0.35 μm to 0.43 μm,inclusive and the maximum valley depth Sv is in a range of 1.03 μm to2.37 μm, inclusive, the height of the peaks is averaged and the numberof peaks that protrude from the average surface falls in proportion tothe increase in the number of valleys, so that when the upper electrodeand lower electrode slide against each other the pressure is distributedamong the peaks and the frequency of contact between the peaks and thesurface of the lower electrode is reduced. For this reason, it is clearthat when the maximum peak height Sp and the maximum valley depth Sv arein the respective ranges described above, damage to the surface 41 issuppressed even more reliably.

In this way, according to the transparent conductive film 1, by formingthe transparent conductive layer 4 so that the maximum peak height Spthat shows the surface roughness of the surface 41 is in a range of 0.35μm to 0.43 μm, inclusive, it is possible to cause light to scatterappropriately, and therefore the production of Newton's rings and thelike can be reliably avoided. Also, unlike a transparent conductive filmwhere the maximum peak height Sp is large (the transparent conductivefilm 1D described above), by setting the maximum peak height Sp in arange of 0.35 μm to 0.43 μm, inclusive, the heights of the peaks can beaveraged, so that when the upper electrode and the lower electrode slideagainst each other, the pressure is distributed among the peaks and itis therefore possible to reliably reduce damage to the surface 41.Accordingly, with a touch panel in which the transparent conductive film1 is incorporated, it is possible to reliably prevent the production ofNewton's rings and to sufficiently improve durability.

Also, according to the transparent conductive film 1, by forming thetransparent conductive layer 4 so that the maximum valley depth Sv thatshows the surface roughness of the surface 41 is in a range of 1.03 μmto 2.37 μm, inclusive, it is possible to cause light to scatterappropriately, and therefore the production of Newton's rings and thelike can be reliably prevented. Also, unlike a transparent conductivefilm where the maximum valley depth Sv is small (the transparentconductive film 1D described above), by setting the maximum valley depthSv in a range of 1.03 μm to 2.37 μm, inclusive, it is possible to reducethe number of peaks proportionate to the increase in the number ofvalleys, so that when the upper electrode and the lower electrode slideagainst each other, it is possible to reliably reduce damage to thesurface 41. Accordingly, with a touch panel in which the transparentconductive film 1 is incorporated, it is possible to reliably preventthe production of Newton's rings and to sufficiently improve durability.

According to the transparent conductive film 1, by forming thetransparent conductive layer 4 so that the maximum peak height Sp thatshows the surface roughness of the surface 41 is in a range of 0.35 μmto 0.43 μm, inclusive, and the maximum valley depth Sv that also showsthe surface roughness of the surface 41 is in a range of 1.03 μm to 2.37μm, inclusive, it is possible to average the heights of the peaks and toreduce the number of peaks proportionate to the increase in the numberof valleys, it is possible to distribute the pressure among the peakswhen the upper electrode and the lower electrode slide against eachother and to lower the frequency of contact between the peaks and thesurface of the lower electrode. As a result, it is possible to reducedamage to the surface 41 more reliably. Accordingly, with a touch panelin which the transparent conductive film 1 is incorporated, it ispossible to reliably reduce the production of Newton's rings and thelike and to significantly improve durability.

Also, with the transparent conductive film 1, by constructing thetransparent conductive layer 4 by compressing conductive fine particles,it is possible to increase the points of contact between the conductivefine particles and to increase the contact area, thereby increasing thestrength of the transparent conductive layer 4 and improving the lighttransmittance of the transparent conductive layer 4. Also, bycompressing the conductive fine particles, unlike the conventionalmethod of manufacturing, it is possible to form the transparentconductive layer 4 without adding resin as a binder, and therefore it ispossible to reduce the probability of a fall in conductivity due tocontact between the conductive fine particles being obstructed by thebinder.

Note that the present invention is not limited to the constructiondescribed above. For example, although an example where the transparentconductive film 1 as a transparent conductor according to the presentinvention is used as the upper electrode of the touch panel 30 has beendescribed, it should be obvious that the present invention can be usedas the lower electrode of the touch panel 30. In addition, although anexample where the transparent conductive layer 4 is disposed (formed) onthe support 2 via the resin layer 3, the present invention can beapplied to a transparent conductive film where the transparentconductive layer 4 is disposed (formed) directly on the support 2. Also,although an example where the transparent conductive layer 4 is formedby compressing a layer of conductive fine particles has been described,the compressing process can be omitted as appropriate in accordance withthe type and size of the conductive fine particles.

1. A transparent conductor, comprising: a film-shaped or plate-shapedsupport; and a transparent conductive layer that is disposed on thesupport and has a surface formed as a rough surface, wherein the surfaceof the transparent conductive layer is formed so that a maximum peakheight that shows a surface roughness of the surface is in a range of0.35 μm to 0.43 μm, inclusive.
 2. A transparent conductor, comprising: afilm-shaped or plate-shaped support; and a transparent conductive layerthat is disposed on the support and has a surface formed as a roughsurface, wherein the surface of the transparent conductive layer isformed so that a maximum valley depth that shows a surface roughness ofthe surface is in a range of 1.03 μm to 2.37 μm, inclusive.
 3. Atransparent conductor, comprising: a film-shaped or plate-shapedsupport; and a transparent conductive layer that is disposed on thesupport and has a surface formed as a rough surface, wherein the surfaceof the transparent conductive layer is formed so that a maximum peakheight that shows a surface roughness of the surface is in a range of0.35 μm to 0.43 μm, inclusive and a maximum valley depth that shows thesurface roughness of the surface is in a range of 1.03 μm to 2.37 μm,inclusive.
 4. A transparent conductor according to claim 1, wherein thetransparent conductive layer is constructed by compressing conductivefine particles.
 5. A transparent conductor according to claim 2, whereinthe transparent conductive layer is constructed by compressingconductive fine particles.
 6. A transparent conductor according to claim3, wherein the transparent conductive layer is constructed bycompressing conductive fine particles.